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The Watson–Crick model of DNA structure provided the final key to molecular genetics

المؤلف:  Zlatanova, J., & van Holde, K. E.

المصدر:  Molecular Biology: Structure and Dynamics of Genomes and Proteomes (2023)

الجزء والصفحة:  2nd Edition , p30-31

2026-10-06

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By 1955, two years after Watson and Crick’s publication of the DNA double-helix model, the molecular basis of genetics was clear. Genes are made of DNA, which is carried in chromosomes. Bacteria and phage have haploid chromosomes, constituted of one or a few double-helical DNA molecules. These simple systems provided the entry into molecular genetics and key ideas for molecular biology. Most eukaryotes have two copies of double-helical DNA in each somatic cell but only one in each gamete. When cells replicate, DNA is duplicated by copying each of the strands of the double helix. As DNA replication occurs independently in each cell of a cellular population, at any point in time some cells will have DNA content characteristic of the G1 phase, before replication begins; other cells will be in the process of replicating their DNA, in the S phase; and still others will have their DNA replicated, in the G2 phase. The distribution of cells in the different stages of the cell cycle can be monitored by flow cytometry (Box 2.4). Mutations occur by modification of DNA sequences, and exchange of alleles occurs by recombination. Almost none of the details or control of these processes were understood in 1955. Much has been learned since then.